Please refer to FIG. 1, which shows a fixture of a conventional projection system 10 for fixing the components of the projection system 10 such as a lamp, a color wheel, an integration rod, a light valve, a projection lens and so on. The fixture includes a lamp frame 111 and an optical engine main body 12, the lamp frame 111 contains a lamp 11, and an optical engine main body 12 is used to fix the optical components except the lamp 11 (for example: the color wheel, the integration rod, the light valve, the projection lens and so on). By the connection of the lamp frame 111 and one end of the optical engine main body 12, a projection system 10 is formed. Because the most components of the projection system 10 such as the lamp, the integration rod, the light valve and so on generate or accumulate heat when they are in use, thus, generally the lamp frame 111 and the optical engine main body 12 are made of metal material in order to sustain or take away the generated heat. The main heat source of the projection system 10 is from the lamp 11, and conventionally the optical engine main body 12 and the lamp frame 111 both of metal material are connected, thus the heat generated by the lamp 11 is conducted through the lamp frame 111 to the light valve and the projection lens of the optical engine main body 12. Therefore, some heat is accumulated on the light valve and the projection lens, and causes the malfunction of the light valve and decreases the image quality projected by the projection lens and reduces the lifetime of the light valve and the projection lens.
According to the demand of the high luminance of the projection system 10, the power of the lamp 11 is also raised, and then the above problems will be more serious. The conventional solution is to dispose a heat sink with large area on the light valve or a fan system to force heat dissipation. But the above solution not only increases the total weight and cost of the projection system 10 but also has poor performance of heat dissipation for the light valve and the projection lens.